A recharge model for high altitude,arid, Andean aquifers

Evidence for groundwater recharge in arid zones is mounting, despite early ideas that recharge was unlikely where evaporation greatly exceeded precipitation. The mechanisms and magnitude of groundwater recharge in the Andes and Atacama Desert are not well known but the subject of current research. Diffuse recharge is expected to be limited to high altitude areas with coarse‐grained soils devoid of vegetation. A recharge model for this environment is developed based on a simple soil moisture budgeting technique and the calculation of actual evaporation based on empirical studies. The model is run with data for the Linzor basins, over 4000 m elevation at 22·2°S on the west slope of the Andes. It is checked against independent estimates based on the chloride mass balance (CMB) method and flood events measured downstream in the Río Salado and found to provide robust and reliable results. The results indicate that irregular and volumetrically limited amounts of diffuse recharge occur at high elevations in half of all years, with a tendency to cluster during La Niña episodes. For the Linzor Basins, mean annual recharge is found to be equivalent to 28 mm a^?1, although no recharge occurs in years with precipitation less than 120 mm, and increases proportionately with annual rainfall amounts above this limit. Copyright © 2009 John Wiley & Sons, Ltd.     

全球变暖减速与郭增建的“海震调温假说”

数值计算表明,潮汐形变和潮汐震荡是海流循环和季节性厄尔尼诺现象发生的原因.2004年12月26日印尼地震海啸后,全球低温冻害和暴雪灾害频繁发生.气候潮汐循环说和"深海巨震降温说"是一种合理的解释,2005～2008年全球气温因为强潮汐和地震海啸而降低.西方科学家也承认了这一客观事实:过去两年里,自然气候的变化抵消了全球气候变暖效应并将继续促使气温在2008年保持缓慢变化的趋势.气候潮汐循环说和海震调温说,阐明了冷气候、强潮汐和强震相互对应的物理机制,对2000年地球进入拉马德雷冷位相后的气候预测有重大科学意义.中国连续18年暖冬的终结是2000年地球进入拉马德雷冷位相和印尼发生地震海啸的合理结果.规律表明,在拉马德雷冷位相时期,全球强震、低温、飓风伴随拉尼那、全球性流感伴随厄尔尼诺将越来越强烈.地球自转、最强潮汐和特大地震都有准四年周期.特大地震可能发生在2000～2030年拉马德雷冷位相时期中的前18年左右.     

与厄尔尼诺和拉尼娜相联系的中国南方冬季降水的年代际异常特征

利用NCEP/NCAR再分析大气环流资料、哈得来中心海温资料、中国700多站降水资料以及全球格点降水资料,详细分析了中国南方冬季降水异常的特征,并揭示了其所对应的欧亚大气环流和东亚冬季风异常与ENSO事件的联系,以及ENSO暖/冷位相对其影响的非对称性。研究进一步证明了厄尔尼诺是导致中国南方冬季降水偏多的重要外强迫因子,并指出拉尼娜对中国南方冬季降水的影响表现出明显的年代际变化特征。1980年之前的拉尼娜年冬季,东亚冬季风显著偏强,东亚大槽偏深,西北太平洋副热带高压偏弱偏东,中国南方受一致偏北风影响,气温偏低,降水偏少,多表现为冷干的气候特征。但1980年之后的拉尼娜年冬季,东亚大槽偏弱,印缅槽偏强,同时在菲律宾以西激发出异常气旋性环流,使得异常偏东风控制中国南方,有利于热带水汽输送增强,因此降水偏多。同时,1980年之后的拉尼娜事件还使得东亚副热带西风急流偏强偏北,中国南方处于急流入口区的右侧,通过二级环流使得中国南方上空的上升运动偏强,有利于降水偏多。因此,1980年之后的拉尼娜年冬季,中国南方易表现出冷湿的气候特征,有时也容易发生低温雨雪冰冻灾害。进一步分析表明,1980年以后拉尼娜成熟期海温异常空间分布型的变化,以及北半球大气环流的年代际变化可能是导致拉尼娜对东亚大气环流的影响在1980年之后发生变化的重要原因。     

西太平洋暖池次表层海温一场与ENSO关系的CGCM模拟结果

全球大气与热带太平洋相耦合的数值模式（ＣＧＣＭ） 很好地模拟了ＥＮＳＯ （ 厄尔尼诺和拉尼娜） 型海表水温（ＳＳＴ） 异常, 进一步分析多年的模式积分结果, 清楚地表明赤道中东太平洋ＳＳＴ 异常与西太平洋暖池次表层（ 深１００ ～２００ ｍ） 的海温异常有密切的关系。在Ｅｌ Ｎｉｎｏ 事件发生之前的半年到一年左右, 西太平洋暖池次表层海温有明显正异常,并向东传播; 而在Ｌａ Ｎｉｎａ 发生之前的半年到一年左右, 暖池次表层海温有明显负异常, 并向东传播。因此, 西太平洋暖池次表层海温异常及其东传对Ｅｌ Ｎｉｎｏ （Ｌａ Ｎｉｎａ） 的发生有极重要作用。     

近百年ElNino/LaNina事件与北京气候相关性分析

通过对近百年El Nino/La Nina事件与北京气候相关性研究发现，El Nino/La Nina事件与北京夏季（6－8月）降水、平均最高气温（7月）和冬季（1月）平均最低气温之间相互关系显著。El Nino事件与夏季降水、冬季平均最低气温呈负相关，与夏季平均最高气温呈正相关，造成降水减少，气温年较差较大，大陆性增强的气候特点。La Nina事件与夏季降水、冬季平均最低气温呈正相关，与夏季平均最高气温呈负关，使降水增加，气温年较差减小，大陆性减弱的气候特点。     

大气环流模式对ENSO时间尺度风应力距平的模拟

通过与观测作比较。评估低分辨率的大气环流模式模拟的风场，模式风场是使用观测海温场外强迫，从１９７９年到１９８８年共积分十年得到的，模式输出为月平均值。结果表明，模式能够相当真实地模拟出风距平场的演变，用风应力距平强迫简单模式，积分十年（１９７９－１９８８），得到的海温距平场（月平均值）和观测海温距平场作比较，模式结果较真实地模拟了１９８２－１９８３年及１９８６／１９８７年暖事件的赤道地区海温距平场     

北半球季节内振荡经向分布及异常的分析

通过诊断分析研究了北半球中高纬大气低频振荡随纬度的变化特征,利用1950-2005年北半球20—75°N逐日500hPa位势高度场资料分析了功率谱。结果表明,（1）大气低频周期随纬度变化,夏季低频周期在45°N有最大值,为52．6d,在低纬和高纬低频周期较小;冬季低频周期最大值位于35°N,为49．9d,最小值位于60°N。（2）无论E1Nino年还是LaNina年,低频周期随纬度变化幅度在夏季都较正常年剧烈,最大振幅达到30d,而对冬季影响不大。原本位于35°N的最长低频周期在LaNina年移至65°N。（3）E1Nino年和LaNina年,低频周期随纬度平均值在冬、夏季差异不大;而在正常年份和所有年份,低频周期随纬度平均值在冬、夏季差异明显。（4）就北半球平均而言,无论ElNino年、LaNina年、正常年还是所有年,夏季低频周期都要小于冬季;ElNino（LaNina）事件在冬、夏季都有使大气低频周期缩短（延长）的趋势。     

A STUDY OF CLIMATOLOGICAL ASPECTS OF FLOW FIELD AND HEAT EXCHANGE ON TROPICAL PACIFIC SURFACE IN THE EL NINO AND LA NINA EVENTS

In this paper, based on the 2°× 2° grid data COADS from 1950—1987 the flow field and heatexchange anomalies on the tropical (11°S—11°N, 120°E—80°W) Pacific surface (TPS) are studiedin El Nino and La Nina events. During E1 Nino, the zonal pressure gradient and the trade windsdecrease on the TPS, the tropical convergence strengthens on the TPS, especially on the centralTPS, the sensible and latent heat exchanges increase, the net longwave radiation and incident solarradiation decrease and the net gain (loss) of heat reduces (increases) on the central and easternTPS. During La Nina the results turn out the contrary. Finally, two feedback mechanisms whichinclude the dynamic, thermal and hydrological processes during E1 Nino and La Nina are summa-rized and a conceptive model for El Nino-La Nina cycle is given.     

2008年初呼和浩特地区持续低温、降雪成因分析

利用常规气象观测资料、以及国家气候中心的海温监测资料等,对2008年初呼市地区出现低温降雪天气的强度、范围、持续时间和灾害影响作了初步分析,并与历史同期进行了比较。分析表明:此次低温降雪天气是在近年来最严重的一次"拉尼娜"事件背景下发生的,与欧亚地区持续大气环流异常密切相关,在"北脊南槽"和西太平洋副高偏北偏强的形势下,北方冷空气不断南下,同时印度洋和孟加拉湾暖湿气流源源不断地往北到东北方向输送,冷暖气流在我国中东部地区频繁交汇,造成了我市持续低温、降雪异常偏多。     

An Isentropic Mass Circulation View on the Extreme Cold Events in the 2020/21 Winter

Three extreme cold events successively occurred across East Asia and North America in the 2020/21 winter.This study investigates the underlying mechanisms of these record-breaking persistent cold events from the isentropic mass circulation(IMC)perspective.Results show that the midlatitude cold surface temperature anomalies always co-occurred with the high-latitude warm anomalies,and this was closely related to the strengthening of the low-level equatorward cold air branch of the IMC,particularly along the climatological cold air routes over East Asia and North America.Specifically,the two cold surges over East Asia in early winter were results of intensification of cold air transport there,influenced by the Arctic sea ice loss in autumn.The weakened cold air transport over North America associated with warmer northeastern Pacific sea surface temperatures(SSTs)explained the concurrent anomalous warmth there.This enhanced a wavenumber-1 pattern and upward wave propagation,inducing a simultaneous and long-lasting stronger poleward warm air branch(WB)of the IMC in the stratosphere and hence a displacement-type Stratospheric Sudden Warming(SSW)event on 4 January.The WB-induced increase in the air mass transported into the polar stratosphere was followed by intensification of the equatorward cold branch,hence promoting the occurrence of two extreme cold events respectively over East Asia in the beginning of January and over North America in February.Results do not yield a robust direct linkage from La Ni?a to the SSW event,IMC changes,and cold events,though the extratropical warm SSTs are found to contribute to the February cold surge in North America.